By the time the cops show it's not likely they can do much other than get a description of the perp and file a report.

No, he did the wrong thing dude. It takes probably half an hour to call the cops, give a description, and then go on about your day. At least the contractor would know that it wasn't an employee that stole anything.
And I say this as someone who, a year and a half ago, saw a guy breaking into a restaurant and had to be the worst witness ever. It was the middle of the night and it looked like he was just looking into the window or fixing or something and I went and stood across the street for 10 minutes just wondering if he was an eccentric owner/repairman who just stands on recycling bins fixing doors in the middle of the night. But then he went to his car and got a crowbar and started trying to pry the door open and that's when I decided to call the cops. There was also another homeless dude sleeping 20 feet away and in the confusion, I didn't know what happened to him. But the cops bring me closer to give a description and I see a dark skinned dude with white hair and blue clothes and I say it looks like him (I was 50 feet away looking at the back of his head). I give my statement and start walking home again but then cop picks me up and brings me back to see another guy who was at the scene.....who was dark skinned, had white hair, and blue clothes. But looked more like the guy who I saw breaking in. Cops give me a wtf look and I don't know what happened but I'm guessing they sorted out who the car belongs to and who the first officers on the scene drawed their guns on.
But I still did the right thing, and learned for sure how bad eyewitness testimony is. So fuck yo' excuses.